The present invention applies to an aircraft, including a civil carrier airplane, being provided with an electric flight control system. It is known from FR-2,908,219 a particular architecture of such an electric flight control system, with a particular arrangement between a flight managing system and a flight path computer allowing for the exchanges inside said flight control system to be rationalized and simplified.
It is known that a usual architecture for controlling an aircraft control surface, for example a rudder or an elevator, comprises a so-called master computer being intended to generate control orders and to send such control orders to one or more so-called slave computers, filling the function of slaving the control surface(s) following such control orders. Such a usual architecture makes it necessary to implant into the master computer monitoring means for checking whether the issued orders are correct so as to avoid slaving, in the slave computers, the control surfaces following erroneous orders.
Usual monitoring operations plan to compare control orders being computed by two different units and to state the master computer as being out of order, should a deviation occurs (between control orders), higher than the monitoring threshold, said deviation having to be confirmed with time.
However, during a deficiency, until the monitoring threshold is reached and such a deviation is confirmed, an erroneous order continues being applied by slave computers to the control surfaces, leading to bring the latter to erroneous positions, and thereby to abnormally increase aerodynamic stresses on the structure of the control surfaces and of the aircraft.
Moreover, adjusting such usual monitorings does not make it possible to detect low level deficiencies, as the monitoring threshold and time delay should be robust, in particular, with respect to static (use of different sensors) and dynamic (asynchronism, law transition) deviations between both units. Therefore, by way of an illustration, for a control surface such as an elevator of a large capacity airplane, the deficiency of the issued order may lead to erroneous steering angles higher than about ten degrees.